1. Field of the Invention
The present invention relates to a push-button switch mechanism. More specifically, the invention relates to a scissors-type push-button switch comprising a resilient element used to dynamically move a key cap back to the initial state and actuate a switch of a circuit membrane of a keyboard.
2. Description of Related Art
In general, a dome or the like made of rubber is the essential part of a keyboard. The dome is a resilient element used to dynamically move a key cap back to the initial state and used to actuate a switch of a circuit membrane. The dome has to be precisely positioned relative to the site of the switch and the key cap, so that the switch can be properly deformed by the -pressed key cap and then the switch can be precisely turned on.
Accordingly, it is an object of the present invention to provide a push-button switch that solves the above problem by providing a push-button assembly in which the trigger process can be precisely done by a simple pushing action.
The present invention achieves these objects by providing a push-button switch comprising a base plate, a circuit membrane, a key cap, a scissors-type linkage and a resilient element. The base plate has at least a first slide-guiding slot and two first bearing slots formed on its surface, and the circuit membrane is disposed on the base plate and provided with at least one switch. The key cap having an underside provided with a second slide-guiding slot and a second bearing slot formed on the underside. The scissors-type linkage is disposed between the circuit membrane and the base plate and is movable along a specified path between a first position and a second position. The scissors-type linkage has a guiding portion, a first linking bracket provided with at least a first end connected to the first bearing slot and at least a second end connected to the second slide-guiding slot, a second linking bracket coupled with the first linking bracket and provided with at least a third end connected to the first slide-guiding slot and at least a fourth end connected to the second bearing slots. The resilient element, mounted on the scissors-type linkage and used to dynamically move the key cap from the second position to the first position, has a trigger actuated by the guiding portion and used to trigger the switch while the key cap is moved toward the second position.
When the force is applied on the key cap, the key cap is moved toward the switch and the scissors-type linkage is actuated. The scissors-type linkage acts like the movement of scissors moving along the certain path from the first position to the second position in reference to the site of the pivotal axis. At the same time, the cantilever arm is pushed by the guiding portion of the scissors-type linkage and the arc portion is elastically deformed. Then, the trigger is finally pressed on and turns on the switch of the circuit membrane when the pivotal axis arrives at the second position. When the force is released, the deformed arc portion is immediately returned to the initial state and releases the stored energy to dynamically push the scissors-type linkage back to the initial state, and the switch is immediately turned off as the trigger is removed.